/*
prf.c -- Pseudo-Random Function for key material generation
- Copyright (C) 2011 Guus Sliepen <guus@tinc-vpn.org>
+ Copyright (C) 2011-2013 Guus Sliepen <guus@tinc-vpn.org>
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
*/
-#include "system.h"
+#include "../system.h"
+
+#include <openssl/obj_mac.h>
#include "digest.h"
-#include "prf.h"
+#include "../digest.h"
+#include "../prf.h"
/* Generate key material from a master secret and a seed, based on RFC 4346 section 5.
- We use SHA512 and Whirlpool instead of MD5 and SHA1.
+ We use SHA512 instead of MD5 and SHA1.
*/
-static bool prf_xor(int nid, char *secret, size_t secretlen, char *seed, size_t seedlen, char *out, ssize_t outlen) {
- digest_t digest;
-
- if(!digest_open_by_nid(&digest, nid, -1))
+static bool prf_xor(int nid, const char *secret, size_t secretlen, char *seed, size_t seedlen, char *out, ssize_t outlen) {
+ digest_t *digest = digest_open_by_nid(nid, -1);
+
+ if(!digest)
return false;
- if(!digest_set_key(&digest, secret, secretlen))
+ if(!digest_set_key(digest, secret, secretlen)) {
+ digest_close(digest);
return false;
+ }
- size_t len = digest_length(&digest);
+ size_t len = digest_length(digest);
/* Data is what the "inner" HMAC function processes.
It consists of the previous HMAC result plus the seed.
while(outlen > 0) {
/* Inner HMAC */
- digest_create(&digest, data, len + seedlen, data);
+ if(!digest_create(digest, data, len + seedlen, data)) {
+ digest_close(digest);
+ return false;
+ }
/* Outer HMAC */
- digest_create(&digest, data, len + seedlen, hash);
+ if(!digest_create(digest, data, len + seedlen, hash)) {
+ digest_close(digest);
+ return false;
+ }
/* XOR the results of the outer HMAC into the out buffer */
for(int i = 0; i < len && i < outlen; i++)
outlen -= len;
}
- digest_close(&digest);
+ digest_close(digest);
return true;
}
-bool prf(char *secret, size_t secretlen, char *seed, size_t seedlen, char *out, size_t outlen) {
- /* Split secret in half, generate outlen bits with two different hash algorithms,
- and XOR the results. */
-
+bool prf(const char *secret, size_t secretlen, char *seed, size_t seedlen, char *out, size_t outlen) {
+ /* This construction allows us to easily switch back to a scheme where the PRF is calculated using two different digest algorithms. */
memset(out, 0, outlen);
- return prf_xor(NID_sha512, secret, secretlen / 2, seed, seedlen, out, outlen)
- && prf_xor(NID_whirlpool, secret, secretlen / 2, seed, seedlen, out, outlen);
+ return prf_xor(NID_sha512, secret, secretlen, seed, seedlen, out, outlen);
}